<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .container{
            width: 800px;
            height: 600px;
            border: 10px solid black;

            /*1. 使用 flex 布局*/
            display: flex;
            /*2. 设置主轴方向: 水平(X), */
            flex-direction: row;
            /*主轴方向垂直: column*/
            /*flex-direction: column;*/
            /*交叉轴: 垂直于主轴*/

        }
        .box{
            width: 200px;
            height: 100px;
            border: 10px solid red;
            margin: 5px;

        }
    </style>
</head>
<body>
    <div class="container">
        <div class="box">

        </div>
        <div class="box">

        </div>
        <div class="box">

        </div>

    </div>
</body>
</html>